The Ross and Yates shafts are critical to science—today and in the future—at Sanford Lab. In this Deep Thoughts, we look at the Ross rehab project and the unique challenges the crews face. Next week, we'll take a look at the importance of top-down maintenance in the Yates.
Rehabbing the Ross Shaft involves much more than pulling out old steel and replacing it with new, although that part is challenging in and of itself. Crews also need to know the terrain of the shaft and understand challenges that may arise—long before work on the project even begins.
In 2017, construction will begin on the Long Baseline Neutrino Facility (LBNF) for the Deep Underground Neutrino Experiment (DUNE). "All the rock that's excavated has to go through the Ross Shaft," said Josh Willhite, LBNF Project Manager. "So it is critical to the success of DUNE."
Recently, the Ross team installed bearing set 159, which sits just below the 2450 Level, or 2,614.4 feet. "Things are going very well," said Underground Access Director Will McElroy. "We have about 2500 feet to go."
As the crews move through the Ross Shaft, they encounter a variety of situations. For example, while installing set 159CD, the crew discovered a void behind some concrete. Each bearing set requires six saddles to support it; each saddle is held in place by 10 anchors. Crews gad out concrete and rock so the saddles can be properly installed then drill anchor holes and fill them with resin.
"After discussions with engineering, the crew came up with a way to install the saddle anchors safely," said Construction Technician Kip Johnson. "Considering the hazards and difficulty of the job, they were professional and positive. They are doing a fantastic job."
Soon, crews will face the most challenging section of the shaft: The Ross Pillar, a 1,200-foot zone of the shaft. The section is surround by a concrete liner that is up to three feet thick in some places. Homestake mined close to the shaft and used the concrete as extra ground support.
Over the years, normal ground movement in the shaft has caused misalignment from the 2900 Level to the 4100 Level. In some areas, the encroaching concrete bowed the steel in the Ross Pillar, creating what are called "wows."
Sanford Lab called on Golder Associates, a global consulting firm that focuses on ground engineering, and Maptek, a mining software company, to determine how best to approach the issue. Traditional surveying and 3-D scans gave the Lab the data it needs to combat the problem. Additionally, the Lab is working with Gordon Revey and Associates to develop a blasting "recipe" that will be useful in removing parts of the concrete liner. In preparation, crews are training and participating in field-testing different recipes.
"The goal is to use this blasting recipe to fracture or crack the concrete to avoid flying debris," McElroy said. 'Then we'll go in with chipping hammers. That's easier on the crews because pneumatic hammers create a lot of noise and vibration."
While the Ross is being rehabbed, the Yates is undergoing top-down maintenance. "They are two very different scopes of work and every time one is impacted, the other is, too," McElroy said. "I don't know of anywhere else in the world where two projects of this scale and this importance are taking place simultaneously, all while operating services underground. People from every department across the SDSTA are making this work."